This application claims benefit of Japanese Application No. 20001-115884 filed in Japan on Apr. 13, 2001, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a photographing lens apparatus, and more particularly to a photographing lens apparatus equipped with a lens barrel that includes multiple lenses and multiple frame members respectively retaining the multiple lenses, and a shift mechanism that appropriately moves part of the frame members in an optical axis direction.
2. Description of the Related Art
In recent years, electronic still cameras (hereafter referred to as xe2x80x9celectronic camerasxe2x80x9d) have become widely popular. An electronic camera is equipped with an electronic photographing device (hereafter referred to as xe2x80x9cphotographing devicexe2x80x9d that receives a subject image that is formed on a specified light receiving surface by a photographing lens apparatus including a plurality of optical elements, and records image signals of still pictures outputted from the photographing device, and picture data corresponding to the image signals in a recording media by means of a predetermined recording device.
A conventional electronic camera is equipped with a photographing lens apparatus that performs a zooming operation and a focusing operation by moving part of the frame members that retain multiple lenses in an optical axis direction prior to a photographing operation.
Also, some of the known conventional electronic cameras are equipped with a barrel retracting type photographing lens apparatus that stores part of the photographing lens apparatus, for example, a photographing lens barrel thereof inside the electronic camera when photographing operations are not performed, for example, when the camera is being carried or stored.
In a photographing lens apparatus, in which multiple lenses retained by multiple frame members are appropriately moved in a direction along its optical axis to perform a zooming operation, a focus adjustment (AF) operation or a barrel retracting operation, relative deviations may occur among arrangements of the optical axes of the lenses retained by the respective moveable frame members as the frame members are moved. When deviations in the optical axes occur, substantial deteriorations in the optical performance, such as, deformations of subject images that are focused, lowered resolutions of obtained images and the like may occur. Therefore, in the photographing lens apparatus having moveable frame members (hereafter referred to as xe2x80x9cmoveable framesxe2x80x9d), it is necessary to restrain deviations in the optical axes that may occur when the frame members move.
A conventional mechanism to move the frame members in a photographing lens apparatus includes for example, a combination of a shaft disposed in parallel with the optical axis and a bearing section (sleeve) engaged with the shaft to achieve desired shift amounts and precision. In the photographing lens apparatus, the shaft is fixed to one of a fixed frame that does not move and a moveable frame that is moveable with respect to the fixed frame, and a bearing section, which engages and guides the moveable frame in a linear advancement direction, is provided on the other (the frame member to which the shaft is not fixed).
An engaging section is provided at one place on one of the fixed frame and the moveable frame to restrict rotation thereof with respect to the other frame member, and a section to be engaged is provided on the other frame member at a location corresponding to the engaging section, which engages the engaging section to cause a state in which the fixed frame and the moveable frame do not rotate relatively with respect to each other. By the structure described above, the conventional photographing lens apparatus practically achieves a sufficient level of suppressing deviations in the optical axes among the mutual lenses.
When the conventional photographing lens apparatus uses the system in which the shaft and the bearing section are disposed on the fixed frame and the moveable frame, respectively, the frame members on which the shaft and the bearing section are disposed need to be manufactured and assembled with high precision. In other words, when the shaft is assembled to the frame member, they must be securely attached to the frame member such that the axial direction of the shaft coincides with a direction along the optical axis of the lens that are retained by the frame member on which the shaft is attached.
To secure such an assembly accuracy of the shaft, a mounting section therefore needs to be provided with a sufficient size, wherein the mounting section is provided at a specified location of the frame member on which the shaft is mounted. However, when the shaft mounting section is made sufficiently large, the size of the frame member unavoidably becomes larger, and therefore it is practically difficult to provide a photographing lens apparatus that realizes miniaturization without deteriorating its optical performance.
A photographing lens apparatus in accordance with the present invention includes an object lens retaining frame that integrally retains a plurality of lenses of different apertures and a diaphragm member disposed between a lens of a large aperture located at a front most position and a lens of a smaller aperture located at a position in the rear of the front most position among the plurality of lenses of different apertures, a first moveable lens frame that is moveable in a photographing optical axis direction and has a mounting section to which the object lens retaining frame is mounted and a shaft fixing section to which a shaft extending in parallel with the photographing optical axis direction is affixed, and a second moveable lens frame having a sleeve that freely, slidably engages the shaft and allows a group of moveable lenses different from the plurality of lenses of different apertures to move in the photographing optical axis direction. The shaft fixing section has at least a portion overlapping a projected plane defined by an external shape of the lens of a larger aperture retained by the object lens retaining frame as viewed from a front face side of the lens of a large aperture and is provided at a specified location within a region adjacent to an outer peripheral section of the lens of a smaller aperture.
Accordingly, in the photographing lens apparatus in accordance with the present invention, attention is paid to an aspect in which the moveable lens frame is equipped integrally with the plurality of lens of different apertures. By so doing, differences in the lens apertures resulting from the plurality of lenses are utilized to thereby provide the shaft fixing section on the inner side of the moveable lens frame (the lens retaining frame and the lens frame retaining member), and further the diaphragm member is provided between the lens of a large aperture and the lens of a smaller aperture among the plurality of lenses of different apertures. As a result, light fluxes incident upon the plurality of lenses are controlled, and at the same time the shaft is shielded such that it cannot be visually recognized when viewed from the front face side of the apparatus.
Accordingly, miniaturization of the apparatus can be readily achieved without affecting the quality of subject images; component parts within the apparatus are not visually recognized when viewed from the front side of the photographing lens apparatus; and unnecessary light incidence or internal reflection are suppressed, such that the optical performance of the apparatus is not deteriorated, and the degree of freedom in designing the external appearance is high.
The objects and advantages of the present invention will become further apparent from the following detailed explanation.